User blog comment:JayAaerow/Administrative Blog: Finding Sources/@comment-7738747-20150218221522

Buddy, I'm sorry.I found the Itsuno's interview which had Dante's age in DMC3, but it's 404 as I feared, but you can still find the links in DMC3 wikipedia page.

Dante is 28/29 years old in DMC1. Kamiya was asked in twitter about Dante's age and he answered "the same as Cobra". Cobra was 29 years old as seen in his tombstone, when his death was faked.

DMC1 was not canon even when it was written since there were major discrepancies : DMC1 says Nero Angelo was a guy with honor, Gilver was anything but honorable: killed a defenseless old lady, killed all Dante's acquaintances or invoked demons to do his dirty job. ( just to mention some differences.)

That DMC1 comic is basically non canon too, a lot of inconsistencies there too: Enzo is a tall fat barman, Vergil actually speaks, it insinuates Sparda just  turn against Mundus because of Eva ( which is not true, later games and media says he first he saves humanity and only MUCH later meet and marries Eva, Trish was basically a sexual object to get on Dante's pants, Dante has a serious inferiority complex towards Vergil and Eva really prefered Dante.